removed but still mentioned betai and spchol2inv in 3.8

[Andreas Weber]

Dear maintainers, sorry for the late post.
Following 2 functions which were removed in 3.8 but still used in the
documentation or in error messages. I havend provided a patch yet
because I need some help to figure out what the right way is.

hg id c6891317ff27

betai:
./scripts/statistics/tests/manova.m:37:## (Currently NOT because the
fcdf respectively betai code is too bad.)

Should we just remove the "betai" part and keep the "bad fcdf code" part?

spchol2inv was removed and chol2inv now also handles sparse matrix:
./liboctave/numeric/SparsedbleCHOL.cc:64:
 ("spchol2inv requires triangular matrix");
./liboctave/numeric/SparsedbleCHOL.cc:67:
 (*current_liboctave_error_handler) ("spchol2inv requires square matrix");
./liboctave/numeric/SparseCmplxCHOL.cc:64:
 ("spchol2inv requires triangular matrix");
./liboctave/numeric/SparseCmplxCHOL.cc:67:
 (*current_liboctave_error_handler) ("spchol2inv requires square matrix");

So a call to chol2inv shows an error "spchol2inv ...."

octave:9> chol2inv(sparse(ones(2)))
error: chol2inv: spchol2inv requires triangular matrix
octave:9> chol2inv(sparse(i*ones(2)))
error: chol2inv: spchol2inv requires triangular matrix
octave:9> chol2inv(sparse(i*ones(2,3)))
error: chol2inv: spchol2inv requires square matrix
octave:9> chol2inv(sparse(ones(2,3)))
error: chol2inv: spchol2inv requires square matrix

Should we just remove "spchol2inv" or is it important for the user to
remind him, that he called chol2inv with a sparse matrix?

Regards, Andy